1. Field of Invention
The invention relates to a driving device and a driving method thereof, and in particular, to a driving device of a brushless DC motor for a fan and a driving method thereof.
2. Related Art
FIG. 1A is a schematic illustration showing a conventional driving device 1A of a brushless DC motor for a fan. As shown in FIG. 1A, the driving device 1A adopts two N-type metal-oxide semiconductor (NMOS) field-effect transistors (FETs) serving as switches to drive the Brushless DC motor. Although the driving device 1A has the advantages of the simple structure and the low price, the driving device 1A has the lower efficiency, and thus disobeys the environment protection concept and the energy saving concept, which are currently emphasized.
In order to enhance the efficiency of the driving device, a driving device 1B with the full-bridge architecture has been proposed. Referring to FIG. 1B, the driving device 1B includes an upper bridge circuit and a lower bridge circuit. The upper bridge circuit is composed of two P-type metal-oxide semiconductor (PMOS) FETs, while the lower bridge circuit is composed of two NMOS FETs.
Although the driving device 1B has the higher efficiency, the behaviors of the PMOS FET on the switching speed and the switching loss cannot be better that those of the NMOS FET. Thus, when the fan with the higher power is applied or the driving technology requiring the higher switching speed is needed, the typically solution is to change the PMOS FETs in the upper bridge circuit into the NMOS FETs.
In order to match with the operation property of the NMOS FET, an integrated driving IC is usually used to control the driving device when the upper and lower bridge circuits are the motor driving devices using the NMOS FETs. However, the integrated driving IC has the higher price, and the operation voltage ranges between 10 to 20 volts. Thus, when the driving power of the selected fan is lower than 10 volts, the integrated driving IC cannot work normally.
Thus, it is an important subject to provide a driving device of a brushless DC motor for a fan and a driving method thereof, so that the simple structure can be obtained, the wider range of the operation voltage can be obtained, and the utility of the driving device and the quality of the motor can be enhanced.